Turbocharged and supercharged engines may be configured to compress ambient air entering the engine in order to increase power. Because compression of the air may cause an increase in air temperature, a charge air cooler (CAC; also referred to as an intercooler) may be employed to cool the heated air, thereby increasing the density of the air and further increasing the potential power of the engine. In one example, the CAC may be a liquid-cooled CAC with coolant flowing through internal cooling tubes of the CAC. As such, a coolant pump coupled to the CAC may be required to control coolant flow through the CAC and thus local CAC cooling. CACs may be used to maintain the charge air at a temperature low enough to increase combustion stability but high enough to reduce condensate formation within the CAC.
However, if overcooling by the CAC occurs, condensation (e.g., water droplets) may form on any internal surface of the CAC that is cooler than the dew point of the compressed air. During transient conditions, such as hard vehicle acceleration, these water droplets may be blown out of the CAC and into the combustion chambers of the engine resulting in increased potential for engine misfire, loss of torque and engine speed, and incomplete combustion, for example.
One approach for controlling the temperature of the CAC in order to reduce the amount of condensation entering the combustion chambers is disclosed in U.S. Patent Application Publication 2003/0056772 by Borrmann et al. In Borrmann, a charge air cooling circuit having a water-cooled CAC, heat exchanger and a coolant pump is provided to cool a temperature of charge air delivered to an internal combustion engine. To modulate the temperature of the charge air, an electrical water pump is provided and is responsive to a regulating unit in communication with a temperature sensor disposed adjacent to the CAC. When the temperature sensor measures a temperature of the coolant, it relays signals to the regulating unit to turn on or off the electrical coolant pump.
The inventors herein have recognized various issues with the above system. In particular, the aforementioned charge air cooling circuit having a water-cooled CAC requires the charge air cooling circuit to be driven by an electric or engine-driven coolant pump. However, this configuration requires additional circuits and energy to drive the coolant pump. Thus, there is added complexity, energy consumption and packaging burdens of said system. As a result, there may be a rise in the cost of manufacturing and overall reduction in fuel economy.
As one example, the issues described above may be addressed by a method for adjusting a coolant flow through a charge air cooler with a single coolant pump based on turbocharger speed, the single coolant pump mechanically driven by rotative power from a turbocharger. In this way, operation of the single coolant pump is powered by rotative power from the turbocharger and operation of the single coolant pump is controlled by turbocharger speed, thereby reducing engine power consumption and control complexity of the engine.
For example, the coolant pump may be mechanically coupled to and thus driven by a rotating shaft of the turbocharger coupling a turbocharger compressor to a turbocharger turbine. As such, the coolant pump is powered by turbocharger speed and a speed of the coolant pump increases with increasing speed of the rotating shaft. The coolant pump may be disposed in a charge air cooling circuit including the charge air cooler (CAC), a low-temperature radiator, and a thermostat valve. As turbocharger speed increases, coolant flow through the CAC increases. Further, as turbocharger speed increases, charge air flow from the compressor and to the CAC also increases. In this way, the CAC may provide the required cooling to the increased charge air flow as turbocharger speed increases. As such, there is a positive, linear relationship between the rotational speeds of the rotating shaft of the turbocharger to which the coolant pump is mechanically coupled and the amount of heated charge air produced by the compressor. Moreover, the system of direct coupling of the coolant pump to the rotating shaft of the turbocharger eliminates the need for additional electrical system (e.g., electrical, battery or engine-driven component) to drive the charge air cooling circuit. As a result, engine control complexity and power consumption may be reduced.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.